This invention relates to novel polymorphic/pseudopolymorphic forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, preferably, L-arginine salt of (2S) 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, having the formula I shown below. The invention also relates to a pharmaceutical composition comprising the novel polymorphic form or their mixture and a pharmaceutically acceptable carrier. The polymorphic forms of the present invention are more active, as antidiabetic and hypolipidemic agent, than the novel 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid. 
The present invention also relates to a process for the preparation of novel polymorphic/pseudopolymorphic Forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, having the formula (I).
The polymorphic Forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, of formula (I) defined above of the present invention lower total cholesterol (TC); increase high density lipoprotein (HDL) and decrease low density lipoprotein (LDL), which have a beneficial effect on coronary heart disease and atherosclerosis.
The novel polymorphic Forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, of formula (I) defined above of the present invention are useful in reducing body weight and for the treatment and/or prophylaxis of. diseases such as hypertension, coronary heart disease, atherosclerosis, stroke, peripheral vascular diseases and related disorders. These novel polymorphic Forms compounds are useful for the treatment of familial hypercholesterolemia, hypertriglyceridemia, lowering of atherogenic lipoproteins, VLDL (very low density lipoprotein) and LDL. The novel polymorphic Forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, of formula (I) of the present invention can be used for the treatment of certain renal diseases including glomerulonephritis, glomerulosclerosis, nephrotic syndrome, hypertensive nephrosclerosis and nephropathy. The novel polymorphic Forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, of formula (I) are also useful for the treatment and/or prophylaxis of insulin resistance (type diabetes), leptin resistance, impaired glucose tolerance, dyslipidemia, disorders related to syndrome X such as hypertension, obesity, insulin resistance, coronary heart disease and other cardiovascular disorders. These novel polymorphic Forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, of formula (I) may also be useful as aldose reductase inhibitors, for improving cognitive functions in dementia, treating diabetic complications, disorders related to endothelial cell activation, psoriasis, polycystic ovarian syndrome (PCOS), inflammatory bowel diseases, osteoporosis, myotonic dystrophy, pancreatitis, arteriosclerosis, retinopathy, xanthoma, inflammation and for the treatment of cancer. The novel polymorphic Forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, of formula (I) of the present invention are useful in the treatment and/or prophylaxis of the above said diseases in combination/con-comittant with one or more HMG CoA reductase inhibitors, hypolipidemic/hypolipoproteinemic agents such as fibric acid derivatives, nicotinic acid, cholestyramine, colestipol, probucol.
Atherosclerosis and other peripheral vascular diseases are the major causes effecting the quality of life of millions of people. Therefore, considerable attention has been directed towards understanding the etiology of hypercholesterolemia and hyperlipidemia and development of effective therapeutic strategies.
Hypercholesterolemia has been defined as plasma cholesterol level that exceeds arbitrarily defined value called xe2x80x9cnormalxe2x80x9d level. Recently, it has been accepted that xe2x80x9cidealxe2x80x9d plasma levels of cholesterol are much below the xe2x80x9cnormalxe2x80x9d level of cholesterol in the general population and the risk of coronary artery disease (CAD) increases as cholesterol level rises above the xe2x80x9coptimumxe2x80x9d (or xe2x80x9cidealxe2x80x9d) value. There is clearly a definite cause and effect-relationship between hypercholesterolemia and CAD, particularly for individuals with multiple risk factors. Most of the cholesterol is present in the esterifed forms with various lipoproteins such as Low density lipoprotein (LDL), intermediate density lipoprotein (IDL), High density lipoprotein (HDL) and partially as Very low density lipoprotein (VLDL). Studies clearly indicate that there is an inverse correlationship between CAD and atherosclerosis with serum HDL-cholesterol concentrations. (Stampfer et al., N. Engl. J. Med., 325 (1991), 373-381) and the risk of CAD increases with increasing levels of LDL and VLDL.
In CAD, generally xe2x80x9cfatty streaksxe2x80x9d in carotid, coronary and cerebral arteries, are found which are primarily free and esterified cholesterol. Miller et al., (Br. Med. J., 282 (1981), 1741-1744) have shown that increase in HDL-particles may decrease the number of sites of stenosis in coronary arteries of human, and high level of HDL-cholesterol may protect against the progression of atherosclerosis. Picardo et al., (Arteriosclerosis 6 (1986) 434-441) have shown by in vitro experiment that HDL is capable of removing cholesterol from cells. They suggest that HDL may deplete tissues of excess free cholesterol and transfer it to liver (Macikinnon et al., J. Biol. Chem. 261 (1986), 2548-2552). Therefore, agents that increase HDL cholesterol would have therapeutic significance for the treatment of hypercholesterolemia and coronary heart diseases (CHD).
Obesity is a disease highly prevalent in affluent societies and in the developing world and is a major cause of morbidity and mortality. It is a state of excess body fat accumulation. The causes of obesity are unclear. It is believed to be of genetic origin or promoted by an interaction between the genotype and environment. Irrespective of the cause, the result is fat deposition due to imbalance between the energy intake versus energy expenditure. Dieting, exercise and appetite suppression have been a part of obesity treatment. There is a need for efficient therapy to fight this disease since it may lead to coronary heart disease, diabetes, stroke, hyperlipidemia, gout, osteoarthritis, reduced fertility and many other psychological and social problems.
Diabetes and insulin resistance is yet another disease which severely effects the quality of a large population in the world. Insulin resistance is the diminished ability of insulin to exert its biological action across a broad range of concentrations. In insulin resistance, the body secretes abnormally high amounts of insulin to compensate for this defect; failing which, the plasma glucose concentration inevitably rises and develops into diabetes. Among the developed countries, diabetes mellitus is a common problem and is associated with a variety of abnormalities including obesity, hypertension, hyperlipidemia (J. Clin. Invest., (1985) 75: 809-817; N. Engl. J. Med. (1987) 317: 350-357; J. Clin. Endocrinol. Metab., (1988) 66: 580-583; J. Clin. Invest., (1975) 68: 957-969) and other renal complications (See Patent Application No. WO 95/21608). It is now increasingly being recognized that insulin resistance and relative hyperinsulinemia have a contributory role in obesity, hypertension, atherosclerosis and type 2 diabetes mellitus. The association of insulin resistance with obesity, hypertension and angina has been described as a syndrome having insulin resistance as the central pathogenic link-Syndrome-X
Hyperlipidemia is the primary cause for cardiovascular (CVD) and other peripheral vascular diseases. High risk of CVD is related to the higher LDL (Low Density Lipoprotein) and VLDL (Very Low Density Lipoprotein) seen in hyperlipidemia. Patients having glucose intolerance/insulin resistance in addition to hyperlipidemia have higher risk of CVD. Numerous studies in the past have shown that lowering of plasma triglycerides and total cholesterol, in particular LDL and VLDL and increasing HDL cholesterol help in preventing cardiovascular diseases.
Peroxisome proliferator activated receptors (PPAR) are members of the nuclear receptor super family. The gamma (xcex3), isoform of PPAR (PPARxcex3) has been implicated in regulating differentiation of adipocytes (Endocrinology, (1994) 135: 798-800) and energy homeostasis (Cell, (1995) 83: 803-812), whereas the alpha (xcex1) isoform of PPAR (PPARxcex1) mediates fatty acid oxidation (Trend. Endocrin. Metab., (1993) 4: 291-296) thereby resulting in reduction of circulating free fatty acid in plasma (Current Biol. (1995) 5: 618-621). PPARxcex1 agonists have been found useful for the treatment of obesity (WO 97/36579). It has been recently disclosed that there exists synergism for the molecules which are agonists for both PPARxcex1 and PPARxcex3 and suggested to be useful for the treatment of syndrome X (WO 97/25042). Similar synergism between the insulin sensitizer (PPARxcex3 agonist) and HMG CoA reductase inhibitor has been observed which may be useful for the treatment of atherosclerosis and xanthoma (EP 0 753 298).
It is known that PPARxcex3 plays an important role in adipocyte differentiation (Cell, (1996) 87, 377-389). Ligand activation of PPAR is sufficient to cause complete terminal differentiation (Cell, (1994) 79, 1147-1156) including cell cycle withdrawal. PPARxcex3 is consistently expressed in certain cells and activation of this nuclear receptor with PPARxcex3 agonists would stimulate the terminal differentiation of adipocyte precursors and cause morphological and molecular changes characteristics of a more differentiated, less malignant state (Molecular Cell, (1998), 465-470; Carcinogenesis, (1998), 1949-53; Proc. Natl. Acad. Sci., (1997) 94, 237-241) and inhibition of expression of prostate cancer tissue (Cancer Research (1998) 58:3344-3352). This would be useful in the treatment of certain types of cancer, which express PPARxcex3 and could lead to a quite nontoxic chemotherapy.
Leptin resistance is a condition wherein the target cells are unable to respond to leptin signal. This may give rise to obesity due to excess food intake and reduced energy expenditure and cause impaired glucose tolerance, type 2 diabetes, cardiovascular diseases and such other interrelated complications. Kallen et al (Proc. Natl. Acad. Sci. (1996) 93, 5793-5796) have reported that insulin sensitizers which perhaps due to the PPAR agonist expression and therefore lower plasma leptin concentrations. However, it has been recently disclosed that compounds having insulin sensitizing property also possess leptin sensitization activity. They lower the circulating plasma leptin concentrations by improving the target cell response to leptin (WO/98/02159). The latest trend that has, of late, crept into the pharmaceutical industry is the studies on polymorphism in drugs and the difference in the activity of different polymorphic forms of a given drug. By the term polymorphism we mean to include different physical forms, crystal forms, crystalline/liquid crystalline/non-crystalline (amorphous) forms. This has especially become very interesting after observing that many antibiotics, antibacterials, tranquilizers etc., exhibit polymorphism and some/one of the polymorphic forms of a given drug exhibit superior bio-availability and consequently show much higher activity compared to other polymorphs. Sertraline, Frentizole, Ranitidine, Sulfathiazole, Indomethacine etc. are some of the important examples of pharmaceuticals which exhibit polymorphism. Polymorphism in drugs is a topic of current interest and is evident from the host of patents being granted. To cite a few, U.S. Pat. No. 5,700,820 discloses six polymorphic forms of Troglitazone, U.S. Pat. No. 5,248,699 discusses about five polymorphic forms of Sertraline hydrochloride while EP 014590 describes four polymorphic forms of Frentizole. EP 490648 and EP 022527 also deal with the subject of polymorphism in drugs.
With an objective to develop novel polymorphic forms for lowering cholesterol and reducing body weight with beneficial effects in the treatment and/or prophylaxis of diseases related to increased levels of lipids, atherosclerosis, coronary artery diseases, Syndrome-X, impaired glucose tolerance, insulin resistance, insulin resistance leading to type 2 diabetes and diabetes complications thereof, for the treatment of diseases wherein insulin resistance is the pathophysiological mechanism and for the treatment of hypertension, with better efficacy, potency and lower toxicity, we focussed our research to develop new polymorphic forms effective in the treatment of the above mentioned diseases. Effort in this direction has led to polymorphic forms having the formula (I).
Another objective of the present invention is to provide polymorphic forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, their stereoisomers, their pharmaceutically acceptable solvates and pharmaceutical compositions containing them or their mixtures which may have agonist activity against PPARxcex1 and/or PPARxcex3, and optionally inhibit HMG CoA reductase, in addition to having agonist activity against PPARxcex1 and/or PPARxcex3.
Another objective of the present invention is to provide novel polymorphic forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, their stereoisomers, pharmaceutically acceptable solvates and pharmaceutical compositions containing them or their mixtures having enhanced activities, without toxic effect or with reduced toxic effect.
Yet another objective of the present invention to provide a process for the preparation of novel polymorphic forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, acid, their stereoisomers, pharmaceutically acceptable solvates.
Still another objective of the present invention is to provide pharmaceutical compositions containing novel polymorphic forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, their stereoisomers, solvates or their mixtures in combination with suitable carriers, solvents, diluents and other media normally employed in preparing such compositions.
In our PCT publication No. WO 99/19313 we have described novel xcex2-aryl xcex1-oxy substituted alkylcarboxylic acids of the general formula (a), 
their pharmaceutically salts, their pharmaceutically solvated and their pharmaceutically acceptable compositions containing them. The pharmaceutical salts of the compounds of the general formula (a) includes salts of the organic bases such as guanine, arginine, guanidine, diethylamine, choline, and the like. Particularly the compounds disclosed include 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid. The current interest in the field of polymorphism in drugs prompted us to take up the investigation as to the possibility of polymorphism in such compounds particularly the arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid. Our observations and results form the subject matter of the present invention. We have, due to our sustained research directed towards finding out effective antidiabetic drugs, observed that arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid, exists in different polymorphic forms possessing enhanced anti-diabetic activity. Accordingly we have, in the course of research, prepared and studied at least eleven polymorphic forms of arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid. These polyrmorphs have been designated, by us, as Forms I, II, III, IV, V, VI, VII, VIII, IX, X and the mixture.
The present invention relates to an observation that arginine salt of 3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxypropanoic acid. exhibits polymorphism, which has not been reported till date. The polymorphic Forms I, II, III, IV and V are obtained from different solvents like isopropyl alcohol, acetone, 1,4-dioxane, dimethylsulphoxide, and dimethylformamide respectively. Form VI is obtained by dissolving any form (Form IV) in water and freeze drying. Similarly Form VII is obtained by dissolving any form (Form I-V) in methanol and quick evaporation of the solvent under reduced pressure at 40-60xc2x0 C. Form VIII is obtained by refluxing Form-I in 1,4-dioxane. Form-IX is obtained by refluxing Form-VIII in isopropyl alcohol. Form X is prepared by heating Form I to 185xc2x0 C. and cooling it to room temperature. Form XI is prepared by heating Form X to 175xc2x0 C. and cooling it to room temperature.
From powder X-ray diffraction studies Forms I, II, III, IV, V, VIII, IX and XI are found to be crystalline in nature. Forms VI, VII and X did not give any peaks in X-ray diffraction due to amorphous nature.
DSC of the polymorphic Form I shows melting endotherm at 181xc2x0 C. In the mixture of polymorphic Forms I and X there is an indication to one of the endotherm at 185xc2x0 C. and 181xc2x0 C. Form II displays endotherms at 131xc2x0 C., 166xc2x0 C., 178xc2x0 C., 214xc2x0 C. and 276xc2x0 C. and exotherms at 169xc2x0 C. Form III exhibits melting endotherm 182xc2x0 C. in addition to an exotherm at 168xc2x0 C. Form IV exhibits endotherms at 149xc2x0 C., 164xc2x0 C. and 185xc2x0 C. and an exotherm at 171xc2x0 C. Form V exhibits endotherms at 119xc2x0 C., 164xc2x0 C., 172xc2x0 C. and 185xc2x0 C. in addition to a melting exotherm at 173xc2x0 C. Form VI exhibits exotherm at 157xc2x0 C. and endotherms at 179xc2x0 C. and 183xc2x0 C. Form VII exhibit exotherm at 132xc2x0 C. and, endotherms at 176xc2x0 C. and 184xc2x0 C. Form VIII there was a similar exotherm of Form VI at 158xc2x0 C. and the melting endotherm at 178xc2x0 C., whereas in Form IX there was only one sharp melting endotherm at 176xc2x0 C. Form X displays an exotherm at 163xc2x0 C. and melting endotherm at 184xc2x0 C. Form XI exhibits a melting endotherm at 184xc2x0 C.
All these polymorphic forms were proved to be identical in solution as evident from Nuclear Magnetic Resonance (NMR), Ultra Violet (UV) and Mass spectral data. On the other hand, solid state techniques like Differential Scanning Calorimetry (DSC), Powder X-Ray Diffractometry (XRD) and Infra Red spectroscopy (IR) revealed the difference among these forms.